The Microwave Sintering Technology and Its Application in the Synthesis of ZrB2

1 IntroductionThe microwave is a kind of high-frequency elec-tromagnetic wave, its wave-length is l ~1000mm, thefrequency scope is 0·3 ~300GHz. But in microwavesintering technology the required frequency is mainly2.45 GHz, though there were reports on 28GHz and60GHz.The microwave sintering is to make use of the mi-crowave energy to heat whole materials to sinteringtemperature and realize densifying.The microwave sintering and normal sintering havethe basic difference in principle. In norm…     

Effect of the Synthesis Method on Co-catalysts Based on MCM-41 for the Fischer–Tropsch Reaction

In this work, cobalt catalysts based on ordered mesoporous materials of the MCM-41 type were synthesized and characterized. The synthesis of the catalysts was performed by using different methods: impregnation; incorporation of the metal in the synthesis gel and ionic exchange of the metal by the template. Different characterization techniques were used (N₂ adsorption–desorption, XRD, TPR, SEM and XPS) to study the textural and structural properties of the samples and the metal-support interaction corresponding to each method of synthesis. These samples were tested in the CO Hydrogenation (Fischer–Tropsch Synthesis) by measuring the CO conversion and the selectivity to CO₂ and some groups of hydrocarbons chains. The results show that structural and textural properties as well as the metal-support interactions are affected by the synthesis method. According to this study, catalytic performance is related to the properties of the samples, observing that the metal support interaction highly affects the activity and selectivity of the catalysts.     

Effect of the Mesostructuration of the Beta Zeolite Support on the Properties of Cobalt Catalysts for Fischer–Tropsch Synthesis

The effect of mesostructuration of beta zeolite and of metal loading on the properties of cobalt-based catalysts for Fischer–Tropsch synthesis was studied in this work. The most active catalyst was the mesostructured beta zeolite-supported cobalt (10%), which also showed a low selectivity to methane and the lowest olefin/paraffin ratio.     

Application of the “fusion” approach for the production of highly efficient biocatalysts based on recombinant strains of the fungus Penicillium verruculosum for the conversion of cellulose-containing biomass

Hydrolysis of cellulose-containing biomass mediated by biocatalysts (enzyme preparations, EP) is one of the most advanced and environmentally friendly methods of obtaining a range of useful substances. A new approach to creating recombinant EPs with predefined properties, which consists in applying fusion constructs for the cloning of genes encoding target enzymes, was used in the present study. A number of EPs with different properties was derived from a strain of the fungus Penicillium verruculosum using fusion constructs; these preparations are of interest primarily as additives enhancing the hydrolytic capacity of the basic cellulolytic complex from P. verruculosum. Use of the new EPs in combination with the basic EP from P. verruculosum resulted in an increase of the biocatalytic (hydrolytic) efficiency of the latter towards cellulose-containing raw materials of plant origin. Addition of 20% of the new EP to the basic EP without changing the total EP dose in the reaction mixture resulted in a significant (up to 70%) increase of the efficiency of hydrolysis of cellulose-containing substrates (ground aspen wood and shredded deresined pine wood).     

Application of Artificial Neural Networks for the Analysis of Data on Liquid–Liquid Equilibrium in Three-Component Systems

Theoretical Foundations of Chemical Engineering - The potential use of artificial neural networks to describe liquid–liquid phase equilibria in ternary systems under polythermal conditions is...     

Effects of KF Loading on Mg–Al Mixed Oxides for the Selective Synthesis of Trimethylolpropane Triesters

A series of Mg–Al hydrotalcites (HTCs) calcined at different temperatures were evaluated for their suitability as solid base catalysts for the selective synthesis of trimethylolpropane triesters (TMPTEs) via transesterification of trimethylolpropane (TMP) with a mixture of C₈–C₁₀ fatty acid methyl esters (FAMEs). The effect of potassium fluoride (KF) loading of the calcined HTCs on the physicochemical and catalytic properties of the materials attained was ascertained. Using a 5?wt% catalyst loading and a FAME:TMP molar ratio of 3.5:1 at 170°C for 8?h, the Mg–Al mixed oxide obtained by calcining HTC at 500°C (HTC-500) gave the highest TMPTE selectivity and FAME conversion. Impregnating HTC-500 with 10?wt% KF (KF/HTC-500) generated strongly basic KMgF₃, KOH, K₂O, and coordinatively unsaturated F^? sites. The FAME conversion and TMPTE yield obtained over different HTC and KF/HTC-500 catalysts depended on their total basicity, where a basic strength of 15?H_{_}?3, a common homogeneous base for the polyol ester production.     

Analysis on the Reasons for the Rapid Rise of China’s Newly-Emerged Cosmetic Brands

China’s leading cosmetic brands,such as CHANDO,Proya,Marubi,Herborist,etc.,have mostly been established in the first decade of the 21st century and in development since then.These brands take nearly 20 years to arrive at their current revenue scale.However,the author noticed that in recent years some new prominent brands have successively emerged in China’s domestic cosmetics industry,for example,HFP,Perfect Diary,Florasis,Judydoll,ZEESEA,MEIKING,etc.,whose revenue scales have caught up with the aforementioned leading brands in merely 3 to 4 years.     

Study on Synthesis of Chitosan Coated Cellulose to the Adsorption Properties for Au~（3＋）

合成了壳聚糖包覆纤维素（CHCC）吸附剂,其结构经FTIR、元素分析进行表征。研究了对Au3＋的吸附包括pH的影响、吸附动力学、吸附选择性和吸附热力学。结果表明：吸附容量受pH影响较大;液膜扩散是吸附的主控制步骤,pH=3时优先选择吸附Au3＋;吸附热力学符合Freundlich模型。-NH2、-OH参与对Au3＋的吸附,树脂中的-CHO可能被Au3＋氧化。     

Allowance for the influence of the stress state on the mechanical characteristics and the coefficients of thermal expansion in Lamé’s problem for a graphite cylinder

The problem of plane strain of a hollow cylinder made of a bimodulus material is considered in a quasi-static constrained formulation. The physical relations allow for effect of the kind of stress state on the mechanical characteristics and the temperature coefficients of linear expansion. Numerical results are presented. Translated from Ogneupory i Tekhnicheskaya Keramika, No. 2, pp. 44–45, February, 2000.     

Synthesis and Dispersion of Dendrimer-Encapsulated Pt Nanoparticles on γ-Al2O3 for the Reduction of NO x by Methane

Dendrimer encapsulated Pt nanoparticles were prepared by using hydroxyl terminated generation four (G4OH) PAMAM dendrimers (DEN) as the templating agents. The encapsulated Pt nanoparticles were dispersed on γ-Al₂O₃ at room temperature by impregnation. Pt/Al₂O₃ (DEN) catalysts were then subjected to thermal treatments in oxidizing and reducing atmospheres at different temperatures. These catalysts were characterized by Transmission Electron microscopy (TEM) and In situ Fourier-Transform Infrared (FTIR) spectroscopy. The TEM analysis of the as synthesized catalysts revealed that the Pt nanoparticles were found to be 2–4 nm in size. It is observed that the Pt particle size in 0.5% Pt/Al₂O₃ (DEN) catalyst increased upon thermal decomposition of the dendrimer. The in situ FTIR results suggested that the presence of oxygen and the Pt nanoparticles in the Pt-dendrimer nanocomposite accelerate the dendrimer decomposition at low temperatures. All the catalysts were tested for the reduction of NO _x with CH₄ in the temperature range of 250–500 °C. NO _x reduction efficiency of Pt/Al₂O₃ (DEN) catalysts were compared with the Pt/Al₂O₃ (CON; conventional) catalyst. The conversion of NO _x was started from the low temperatures over Pt/Al₂O₃ (DEN) catalysts. The high selectivity of NO _x to N₂ of 74% was obtained over 0.5% Pt/Al₂O₃ (DEN) catalyst at low temperatures around 350 °C.     

ZSM-5 Supported Cobalt Catalyst for the Direct Production of Gasoline Range Hydrocarbons by Fischer–Tropsch Synthesis

Abstract  

Fischer–Tropsch synthesis (FTS) reaction for the direct production of gasoline range hydrocarbons (C₅–C₉) from syngas was investigated on cobalt-based FTS catalyst supported on the ZSM-5 possessing a four different Si/Al ratio. The FTS catalysts were prepared by impregnation method using cobalt nitrate precursor in a slurry of ZSM-5, and they were characterized by surface area, XRD, H₂-TPR and NH₃-TPD. Cobalt supported catalyst on ZSM-5 having a low Si/Al ratio of 15 was found to be superior to the other catalysts in terms of better C₅–C₉ selectivity due to the formation of small cobalt particle and the presence of larger number of weak acidic sites. It also exhibited the highest catalytic activity because of the higher reducibility and the small cobalt particle size.     

Low-temperature fabrication of sol–gel NiO film for optoelectronic devices based on the ‘fuel’ of urea

In this work, NiO coating is fabricated by a low temperature ‘combustion process’ driven by ‘chemical oven’ on quartz and indium tin oxide (ITO) substrates followed by an annealing process in air at 225 °C for 2 h. The NiO coating is analyzed by means of thermalgravimetric differential thermal analysis (TG-DTA), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electric microscopy (SEM), atomic force microscope (AFM), and UV–visible spectrometer. A prelimilary photovoltaic performance measurement of the fabricated device (ITO/NiO/poly-TPD/PC₇₁BM/Al) shows a short circuit current density (J_sc) of 5.28 mA cm⁻² and power conversion efficiency (PCE) of 1.56% under an illumination of 100 mW cm⁻². The PCE of device with combustion NiO HTLs is almost 10-fold higher than those of the devices based on common NiO HTLs. The combustion fabricated NiO coating may provide an effective approach to fabricate other NiO-based optoelectrical devices at relative low temperature.     

Polymer matrices on the basis of polyacrylamide and β-cyclodextrin-containing pseudorotaxane for prolonged drug release: Synthesis and properties

Polymer cross-linked matrices based on polyacrylamide (PAA) and β-cyclodextrin-pseudorotaxane have been designed. The structure and properties of the objects synthesized were confirmed and studied by a series of methods, involving ultraviolet-, Fourier transform infrared-spectroscopy, thermal mass spectrometry, DSC, X-ray diffraction analysis (WAXS and SAXS). Desorption kinetics (especially significant slowing of desorption process) of some drugs, like metoprolol succinate and loratadine from obtained polymer matrices is shown to be optimal with 10 wt% β-CD-pseudorotaxane in their structure.     

Synthesis of β-SiC in the intermediate layer of corundum coatings based on a sol-gel binder for protecting graphite objects from oxidation

A coating is developed for protecting graphite from oxidation at 2023 – 2223 K. The efficiency of the protective action of a corundum coating based on a sol-gel binder increases due to creating a dense intermediate layer between the graphite substrate and the coating as a result of its self-reinforcement with fibers of mullite crystals and β-SiC nanoparticles. Components of a modifier and sol-gel binder, but not carbon of the graphite substrate, provide synthesis of β-SiC.     

Effect of Different Solvents on the Synthesis of Resorcinol–Formaldehyde and g-C3N4 Composite as Photocatalyst for Degradation of Methylene Blue

Carbon nitride, a hot spot in metal-free material, has been widely studied for various fields of application. Various efforts have been made to improve the photocatalytic activity of carbon nitride, including cross-linking with other kinds of polymers. In this study, Resorcinol – Formaldehyde (RF) resins were chosen to modify carbon nitride because they can act as a sacrificial agent to create the Z-scheme catalytic system with carbon nitride. The novelty of this study is using polyol solvents to synthesize nano-fragments Resorcinol–Formaldehyde. The goal of this work was to study the influence of polyol solvents on the formation of RF polymer and the photocatalytic performance of RF-modified carbon nitride. Scanning electron microscope (SEM) images suggested that nano-fragments RF resins that were synthesized in ethylene glycol and glycerol were able to deposit densely on the surface and in pores of carbon nitride as nano-fragments, while RF obtained from hydrothermal had the morphology of microspheres and only anchored on the surface of carbon nitride. In terms of BET (Brunauer–Emmett–Teller) surface area, E-RFCN had the largest value in four samples (72.3 m² g^?1) and was the only sample that had the BET value higher than that of pristine carbon nitride (26.9 m² g^?1). Regarding the photocatalytic activity, E-RFCN was the optimal sample that could completely remove MB in the solution within 40 min in H₂O₂/visible light conditions. Furthermore, the catalyst could work effectively in a wide pH range from 5 to 9, and could be reused for 4 cycles. By conducting radical scavenging experiments, it was founded that ?OH, photoinduced holes (h?+) and ?O₂^? contributed to MB decomposition by the order: h?+??>??OH?>??O₂^?. Finally, the hypothesis for the effect of polyol solvents on the polymerization of RF and the RF-carbon nitride cross-linking had been proposed.